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At least 1,153 records · Page 64Linked to original sources
PubMed1982

Visual acuity in color contrast on cathode ray tubes: role of luminance, hue, and saturation contrasts.

Three experiments were conducted on 90 flying personnel to determine the role of luminance, hue, and saturation contrasts on angular visual acuity measured on a CRT system. A Snellen E test object was displayed under various visual acuity conditions on a TV screen, in color contrast, using red, yellow, green, cyan, blue, purple, white, and black. The response system gives response times and quality. The three photocolorimetric parameters are classified through data processing. All other things being equal, the best visual acuity is obtained under a luminance contrast. Two groups of colors can be differentiated under a hue contrast. The first group (red, blue, purple) is better perceived than the second (green, cyan, yellow, white) whatever the other color in simultaneous contrast may be. Higher saturation enhances visual acuity. A curve of mean response time vs. test object sizes is established for the various color couples. The obtained results are of interest for aerospace ergonomics.

Adult↗
PubMed1982

Spectral sensitivity and color discrimination changes in glaucoma and glaucoma-suspect patients.

Color vision changes may occur early in the course of glaucoma and may precede visual field loss. Glaucoma suspects, having raised intraocular pressure and no diagnostic optic nerve head or visual field changes, may also have color vision loss. Unfortunately, the instruments used in the studies that have demonstrated these color vision changes were not feasible for routine clinical use; likewise, the studies did not carefully control for the effects of small pupil size and age or did not point to the underlying mechanisms responsible. We studied 19 glaucoma patients, 19 glaucoma suspects, and age-matched controls for each group by means of the Farnsworth D-15 panel test, a desaturated version of the D-15 test, and by measures of spectral increment threshold. Minor modifications of the Farnsworth D-15 panel test produce highly significant differentiation of glaucoma and glaucoma-suspect patients from age-matched normal groups. Further, spectral increment thresholds, with a two-degree spectral target flashed at either 1 or 25 Hz on a bright white background, show that both achromatic and chromatic sensitivity are significantly reduced when compared with their age-matched normals. Pupil size does not seem to be a significant factor. These results suggest that the function of two different ganglion cell populations is affected in glaucoma and that glaucoma may produce functional loss in the central foveal area earlier in the disease process than previously believed.

Adolescent↗
PubMed1980

Color matches of patients with retinitis pigmentosa.

The color matches of 46 retinitis pigmentosa (RP) patients were found to differ significantly from those of 55 unaffected observers. The color matches of group I (trichromatic) RP observers were more protanomalous (i.e., required a greater red/green mixture ratio) than those of unaffected observers. The matches of group II (dichromatic) RP observers were more protanopic (i.e., required less yellow to match the red primary) than those of the group II unaffected observers. In view of current evidence, this difference can be attributed to reductions in the pigment optical density of cone photoreceptors in eyes of RP patients.

Adolescent↗
PubMed1995

The renin-angiotensin system--a possible neuromodulator in the human retina?

Morphology studies imply a possible contribution of the renin-angiotensin system (RAS) to neurotransmission in the mammalian retina. To investigate further the functional role of the RAS in the visual system of humans, we tested the effects of the angiotensin-converting enzyme (ACE) inhibitor Captopril (Capt; 25 mg) on electroretinogram (ERG) recordings, the cone flicker threshold (CFT), the FM-28-HUE test, and the psychophysical rod threshold in healthy volunteers. The parameters of renin, angiotensin, and blood pressure were controlled. We obtained the following results. First, Capt induced a significant decrease in amplitudes of the scotopic b-wave, oscillatory potentials, and the a-wave. The latency of responses to 30-Hz flicker was increased. Second, the CFT was reduced to a lower intensity, whereas the final rod threshold remained unchanged. These results are in accordance with previous immunocytochemical and electrophysiological data. They cannot be explained exclusively by the observed changes in systemic blood pressure. We conclude that the RAS may possibly be involved in retinal neurotransmission in humans in addition to its vascular effects.

Administration, Oral↗